title: Highly thermostable xylanase purified from Rhizomucor miehei NRL 3169.
abstract: A thermostable xylanase was purified and characterized from the thermophilic fungus Rhizomucor miehei (Cooney & Emerson) Schipper. The enzyme was purified to homogeneity by ammonium sulfate precipitation, sephadex G-100 gel filtration and diethylaminoethyl cellulose anion exchange chromatography with a 29.1-fold. The enzyme was highly active within a range of pH from 5.0 to 6.5. The optimum temperature of the purified enzyme was 75°C. The enzyme showed high thermal stability at 70°C and 75°C and the half-life of the xylanase at 90°C was 30 min. Km and Vmax values at 50°C of the purified enzyme were 0.055 mg/ml and 113.5 μmol min⁻¹ mg⁻¹ respectively. The enzyme was activated by Ca²+, Cu²+, K+ and Na+. On the other hand, Ag²+, Hg²+, Ba²+, and Zn²+ inhibited the enzyme. The molecular weight of the xylanase was estimated to be 27 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The present study is among the first works to examine and describe a secreted highly thermostable endoxylanase from the Rhizomucor miehei fungus. This enzyme displays a number of biochemical properties that make it a potentially strong candidate for industrial and commercial application in pulp bleaching.
authors.affiliation: Biological and Geological Sciences Department, Faculty of Education, Ain Shams University, Heliopolis, Roxy, Cairo, Egypt. emanfawzy@hotmail.com
authors.forename: E M
authors.initials: EM
authors.lastname: Fawzi
mesh_terms: D002850:Chromatography, Gel / Q000379:methods; D002852:Chromatography, Ion Exchange / Q000379:methods; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D043364:Endo-1,4-beta Xylanases / Q000302:isolation & purification*; D008970:Molecular Weight; D020103:Rhizomucor / Q000201:enzymology*; D013696:Temperature; D014990:Xylans / Q000378:metabolism
chemical_list: D014990:Xylans; D043364:Endo-1,4-beta Xylanases